Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$199.27	11.802%	$222.7878	$222.79	$222.80	$222.80
Purchase #2	$116.32	10.152%	$128.1288	$128.13	$128.15	$128.10
Purchase #3	$194.66	7.246%	$208.7651	$208.77	$208.75	$208.80
Purchase #4	$123.74	3.520%	$128.0956	$128.10	$128.10	$128.10
Purchase #5	$90.25	5.626%	$95.3275	$95.33	$95.35	$95.30
Purchase #6	$221.25	3.771%	$229.5933	$229.59	$229.60	$229.60
Purchase #7	$99.56	3.504%	$103.0486	$103.05	$103.05	$103.00
7 purchase totals =	$1,045.05		$1,115.7467	$1,115.76	$1,115.80	$1,115.70